Thermostat needle is stuck on the down side of the pin - on the cold side of the display

Three ways to fix it. Disassemble the instrument cluster so you can physically push the needle counter-clockwise to the correct side of the pin. Get the engine hot enough so the pointer would be over half scale. The computer will want to position the pointer there, and the pointer will look for the shortest way there, which would be counter-clockwise. From there it will follow its normal path back down. Find a mechanic with the GM scanner to perform the gauge test. That will run all the gauges to 1/4, 1/2, 3/4, and full scale, then back down. Once the temperature gauge goes to 3/4 scale, it will go back down like normal.

These are not the old-style reliable spring-loaded mechanical gauges like we had in the past. They now have four electromagnets that are pulsed by the computer to position the pointer. When your engine is cold, the pointer is looking for the shortest way to "cold", and that's clock-wise, so it's hitting that pin.